Behold: Science as seeing

One astronomer’s dimpled pie is another’s cratered moon. How can our mind’s eye learn to see the new and unexpected?

When Galileo looked at the Moon through new telescope in early 1610, he immediately grasped that the shifting patterns of light and dark were caused by the changing angle of the Sun’s rays on a rough surface. He described mountain ranges ‘ablaze with the splendour of his beams’, and deep craters in shadow as ‘the hollows of the Earth’; he also rendered these observations in a series of masterful drawings. Six months before, the English astronomer Thomas Harriot had also turned the viewfinder of his telescope towards the Moon. But where Galileo saw a new world to explore, Harriot’s sketch from July 1609 suggests that he saw a dimpled cow pie. Why was Galileo’s mind so receptive to what lay before his eyes, while Harriot’s vision deserves its mere footnote in history?

Learning to see is not an innate gift; it is an iterative process, always in flux and constituted by the culture in which we find ourselves and the tools we have to hand. Harriot’s 6-power telescope certainly didn’t provide him with the level of detail of Galileo’s 20-power. Yet the historian Samuel Y Edgerton has argued that Harriot’s initial (and literal) lack of vision had more to do with his ignorance of chiaroscuro – a technique from the visual arts first brought to full development by Italian artists in the late 15th century.

By Galileo’s time, the Florentines were masters of perspective, using shapes and shadings on a two-dimensional canvas to evoke three-dimensional bodies in space. Galileo was a friend of artists, and someone who in his youth might have considered becoming one himself. He believed with a kind of religious fervour that the creator of the world was a geometer. Galileo likely imbibed these mathematically deep methods of representation, based as they are on the projective geometries of light rays. Harriot, on the other hand, lived in England, where general knowledge of these representational techniques hadn’t yet arrived. The first book on the mathematics of perspective in English – The Art of Shadows by John Wells – appeared only in 1635. When Galileo looked at the face of the Moon, he had no trouble understanding that lunar mountaintops first catch fire with the rising Sun while their lower slopes remain in darkness, just like they do on Earth. Galileo therefore had a theory for what he was seeing when those pinpricks of light winked into existence along the terminator line of day and night; he even used the effect to measure the heights of those mountains, finding them higher than the Alps. Harriot, a brilliant polymath yet possibly blind to this geometry, looked at the same scenes half a year before Galileo, but didn’t understand.

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